The organs which occur in reduced form and are useless to the possessor but were fully developed and functional in its ancestors are called vestigial organs. For example the nictitating membrane in humans is a vestigial organ. It is a small, pinkish, reduced and nonfunctional fold of skin present in the corner of eyes. But it is fully developed and still functional in frog, pigeon and cat even today. This indicates that humans may have evolved from those ancestors who had a functional nictating membrane in the eyes.
In the same way, the functionless vermiform appendix of large intestine is a vestigial organ in humans, while it is still functioning in herbivores such as cow and buffalo. This indicates that the human beings may have evolved from those ancestors who had a functional vermiform appendix.
Test Your Understanding and Answer These Questions:
- What are vestigial organ.
- Give two examples of vestigial organs.
- How do vestigial organ provide evidence for evolution?